Gas-dispensing device with self-contained gas container having a diffusion membrane

ABSTRACT

A gas-dispensing device ( 2 ) for dispensing a gas into breathing gas, comprising a membrane ( 6 ) through which the gas can diffuse into the breating gas, is described. The gas-dispensing device ( 2 ) is simple and reliable because it contains a self-contained chamber ( 4 ) in which the gas is held at a predefined overpressure, and the membrane ( 6 ) is arranged to form a part of the chamber&#39;s ( 4 ) wall.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a gas-dispensing device fordispensing a gas into a breathing gas, of the type having a membranethrough which the gas can diffuse into the breathing gas. The inventionalso is directed to a breathing apparatus having such a gas-dispensingdevice.

2. Description of the Prior Art

In conjunction with respiratory care (with a respirator, ventilator,anesthetic machine or other breathing machine), the physician maysometimes wish to supplement the breathing gas with a medical gas. NO isan example of a medical gas, but there are other gases with atherapeutic or other effect (e.g. anesthetic, analgesic).

One way to dispense a gas is to utilize a membrane permeable to the gas.The rate of diffusion then governs the amount dispensed. Connecting agas source containing the gas to be dispensed into the flow of breathinggas in a breathing apparatus via a membrane is known.

One disadvantage of this system is that the gas source may be bulky.Patient transport then becomes more difficult, or dispensing may need tobe interrupted during transport. The gas source can also require morerigorous safety precautions to ensure that the gas source does not leak.This is the case for e.g. NO and anesthetic gases. In addition, thegas-dispensing system must be equipped to prevent overdosing, even ifthe membrane or some other component (e.g. a pressure regulator) shouldfail.

Another disadvantage of known techniques is that special monitoringequipment, or special pressures combined with fixed valves etc., arerequired if a specific total amount (a given amount of gas) is to bedispensed.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a gas-dispensing devicethat eliminates, at least in part, the problems associated withgas-dispensing devices according to the prior art.

Another objective is to provide a breathing apparatus, which allows thedispensing of a gas into breathing gas in a simple and uncomplicatedfashion that is still safe and accurate.

The first object is achieved in accordance with the invention in agas-dispensing device having a membrane through which gas can diffuseinto breathing gas, and having a self-contained chamber in which the gasto be dispensed is contained at a predetermined overpressure, with themembrane forming a part of the wall of the self-contained chamber.

Instead of a procedure in which a source of gas is connected to a dosingmeans, a self-contained chamber is charged with a specific amount of gasto be dispensed. This is accomplished by filling the chamber with gas ata specific overpressure and closing it. The chamber also contains amembrane through which the gas diffuses. When the chamber is placed inthe flow paths of a breathing apparatus (or when at least the membraneis placed in contact with the flow paths), the enclosed gas iscontinuously dispensed. Since the diffusion is mainly governed by thepartial pressure difference on both sides of the membrane, theoverpressure need not be particularly large.

Gas dispensing can be suitably regulated by covering the membrane with acovering means (preventing leakage before use) that can be removed todiffering extents. This exposes the membrane to varying degrees, and theamount dispensed can thereby be varied. The total amount dispensed cannever exceed the amount held in the chamber.

Pressure in the gas-dispensing device drops as gas diffuses out, therebycausing a drop in the amount dispensed. The rate of decline is virtuallylinear. This could be an advantage in some situations. Some gases needto be dispensed in large quantities initially but in gradually decliningamounts thereafter until no more gas is dispensed. This kind of controlwas previously hard to achieve and demanded constant resetting of valvesor other control components. With the gas-dispensing device according tothe invention, dispensing gas in declining amounts is automatic.

When dispensing needs to be more uniform over a longer period of time,an increasingly large area of the membrane can be uncovered at certainintervals. A large exposed area leads to large diffusion thatcompensates for drops in pressure. However, this does produce somevariation in the amount of gas being dispensed.

A more uniform dispensing of gas is provided when the chamber contains adonor substance for the gas. The donor substance could be a liquid (e.g.anesthetic liquid) or a solid (e.g. an NO donor material). As long asthere is a donor substance present (or as long as the donor substanceprovides the gas), a partial pressure will be sustained.

In order to achieve completely uniform gas dispensing, it isadvantageous for the gas-dispensing device to have a pressure devicethat maintains pressure inside the chamber. One such pressure device canbe e.g. a spring-loaded piston that compresses the gas.

This could also be done when there is a donor substance present in thechamber.

Pressure in the dosage container can be measured with a pressure gauge.The pressure gauge can advantageously be battery-powered.

It would be advantageous during long periods of gas dispensing if thegas-dispensing device were to be equipped with a refill device,particularly when the gas-dispensing device is incorporated into or afixed part of the breathing apparatus.

The refill device can be adapted for refill of gas and/or donorsubstance.

The second object is achieved in accordance with the invention in abreathing apparatus for supplying breathing gas to a patient having agas-dispensing device of the type described above.

Depending on the application, having a separate gas-dispensing deviceplaced in the flow paths may sometimes be unsuitable. The breathingapparatus could then be suitably devised so the gas-dispensing device isa fixed, integral part of the breathing apparatus.

Integrating the gas-dispensing device with a tracheal tube orinspiratory line would then be particularly advantageous.

DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a first embodiment of a gas-dispensing deviceaccording to the invention.

FIG. 2 illustrates a second embodiment of a gas-dispensing deviceaccording to the invention.

FIG. 3 illustrates a third embodiment of a gas-dispensing deviceaccording to the invention.

FIG. 4 is a schematic illustration of a breathing apparatus according tothe invention, indicating locations at which a gas-dispensing deviceaccording to the invention can be located or incorporated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a first embodiment of a gas-dispensing device 2 accordingto the invention. The gas-dispensing device 2 has a closed chamber 4holding a gas, at a predefined overpressure, to be dispensed. A membrane6 is arranged at one end of the chamber 4. The membrane 6 can occupy asmaller or larger part of the chamber 4. Gas inside the chamber 4diffuses out into atmosphere when the membrane 6 is uncovered. When thegas-dispensing device 2 is placed in the flow paths of a breathingapparatus, the gas can be dispensed into a breathing gas. A coveringmeans covers the membrane 6 before the membrane is put into use. Thisprevents leakage of gas before dispensing is to take place.

FIG. 1 shows how the covering means can be formed by different segments8A-C removed, one at a time (one segment has already been removed toshow the membrane), from the chamber 4. The magnitude of the dispenseddose can be selected by exposing the membrane to differing degrees. Forexample, exposure of a small area of the membrane 6 can be selected forneonates, a somewhat larger area for infants etc. up to the largest areafor adults.

Pressure (the partial pressure of the gas) in the gas-dispensing device2 drops as the gas diffuses out through the membrane 6. This leads, inturn, to a drop in the amount of gas dispensed. This is an advantagewith some gases, since it leads to gentler tapering off of medication.However, more uniform dispensing is desirable with other gases. One wayto maintain the amount of gas dispensed is to increase the area ofexposed membrane 6 by removing more segments 8A-C.

FIG. 2 shows a second embodiment of a gas-dispensing device 10. Thegas-dispensing device 10 can be connected to a system of tubing on abreathing apparatus via a first connection end 12A and a secondconnection end 12B. Breathing gas can flow e.g. as designated by thearrow 14.

The gas to be dispensed is in a chamber 16 and is dispensed into theflow of breathing gas 14 via a membrane 18.

A small piston 20 is arranged to compress the gas so as to keep gasdispensing as constant as possible over time. In this instance, thepiston 20 is driven by a spring 22. Relatively constant gas dispensingcan be achieved, as long as any gas is left in the chamber 16, by thechoice of dimensions for the chamber 16 and the piston 20 and the typeof spring 22.

FIG. 3 shows a third embodiment of the gas-dispensing device accordingto the invention, in the form of a tracheal tube 24 in this instance.The tracheal tube 24 has an end 26 devised for insertion into apatient's airways. Gas in a chamber 28 is dispensed via a membrane 30into the breathing gas flowing through the tracheal tube 24. The partialpressure of the gas is maintained for a prolonged time by providing thechamber 28 with a donor substance 29 for the gas. The donor substancecould be a liquid or a solid. As long as the donor substance can providethe gas, an essentially constant dosing of the gas is maintained.

The chamber can be refilled with fresh gas and/or donor substance via arefill nipple 32 when necessary.

FIG. 4 shows one embodiment of a breathing apparatus, in the form of aventilator 34, according to the invention.

The ventilator 34 can be connected to a patient 36 in order to supplyher/him with breathing gas. The breathing gas can consist of one or moregas components. FIG. 4 depicts the ventilator 34 with a first gas inlet38A and a second gas inlet 38B to illustrate this. The gases are mixedin the correct proportions and quantities in a gas regulator 40. Thebreathing gas then flows through an inspiratory channel 42 to aninspiratory line 44. The inspiratory line 44 is connected to a 3-wayconnector 46. The 3-way connector 46 is connected to a tracheal tube 48and to an expiratory line 50. The expiratory line 50 carries breathinggas from the patient, via an expiratory valve 52, to atmosphere or anevacuation (not shown). A control unit 54 controls the ventilator. Othercommon components in the ventilator 34, such as pressure and flowgauges, are not shown in FIG. 4 because they are well known.

A number of examples of where the gas-dispensing device can be placed ormade an integral part of the ventilator 34 is shown for the ventilator34.

Here, a first gas-dispensing device 56A is shown in the inspiratorychannel 42, a second gas-dispensing device 56B is shown connected to theinspiratory line 44, a third gas-dispensing device 56C is shownconnected to the inspiratory line 44 and a fourth gas-dispensing device56D is shown connected to a tracheal tube 48. The second and fourthgas-dispensing devices 56B, 56D can be the gas-dispensing devices shownin FIG. 2 and FIG. 3 respectively.

Combinations of the depicted embodiments are fully feasible. Thus, allthe gas-dispensing devices can be equipped with one or more segmentsaccording to FIG. 1, a piston and spring according to FIG. 2, donorsubstance and a refill nipple according to FIG. 3.

In a similar fashion, the gas-dispensing device according to theinvention can be used with respirators, anesthetic machines, sub-acutedevices (e.g. for home nursing) etc.

Although modifications and changes may be suggested by those skilled inthe art, it is the invention of the inventor to embody within the patentwarranted heron all changes and modifications as reasonably and properlycome within the scope of his contribution to the art.

1. A gas dispensing device for dispensing a gas into a breathing gas,comprising: a self-contained chamber charged with a gas to be dispensedand sealed to maintain said gas at a predetermined overpressure; and amembrane through which said gas can diffuse into breathing gas due tosaid overpressure, said membrane forming a part of a wall of saidself-contained chamber and, after charging of said self-containedchamber with said gas to be dispensed, said self-contained chamberhaving no ingress or egress for said gas other than said membrane; and apressure device for maintaining pressure in said chamber duringdispensing of said gas.
 2. A gas dispensing device as claimed in claim 1comprising a cover for said membrane, allowing said gas to be dispensedonly upon removal of said cover.
 3. A gas-dispensing device as claimedin claim 2 wherein said cover is variable in size, to selectively coverdifferent portions of said membrane to selectively set an amount of saidgas dispensed through said membrane.
 4. A gas-dispensing device asclaimed in claim 1 wherein said chamber contains a donor substance insaid gas.
 5. A gas dispensing device as claimed in claim 1 furthercomprising a refill arrangement in communication with said chamberallowing said chamber to be refilled.
 6. A breathing apparatuscomprising: a source of breathing gas; and a gas dispensing devicedisposed to interact with said source of breathing gas, said gasdispensing device comprising a self-contained chamber charged with a gasto be dispensed and sealed to maintain said gas at a predeterminedoverpressure, and a membrane through which said gas can diffuse intobreathing gas, said membrane forming a part of a wall of saidself-contained chamber and, after charging of said self-containedchamber with said gas to be dispensed, said self-contained chamberhaving no ingress or egress for said gas other than said membrane; and apressure device for maintaining pressure in said chamber duringdispensing of said gas.
 7. A breathing apparatus as claimed in claim 6comprising an inspiratory passage, and wherein said gas dispensingdevice is disposed in said inspiratory passage.
 8. A breathing apparatusas claimed in claim 6 comprising a patient connector, and wherein saidgas dispensing device is disposed in said patient connector.